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REVIEW OF LITERATURE
II. REVIEW OF LITERATURE
Research reports on the effect of variation in dietary profile and
early feed restriction in broilers on various growth parameters and
carcass yields are presented in brief under the following paragraphs.
2.1 Compensatory growth in the broiler chicken
2.2 Factors that influence compensatory growth
2.2.1 Duration and timing of restricted nutrition
2.2.2 Nature and severity of restricted nutrition
2.2.3 Condition of re-alimentation
2.2.4 Genetic factors
2.2.5 Adipose development and fat deposition
2.3 Methods of feed restriction
2.3.1 Physical feed restriction
2.3.2 Diet dilution and chemical methods of feed restriction
2.3.3 Use of low protein or low energy diets
2.4 Effect of dietary variation and feed restriction on performance
2.4.1 Body weight
2.4.2 Feed consumption and feed conversion ratio
2.4.3 Livability of birds
2.5 Effect of dietary variation and feed restriction on carcass
characteristics
2.5.1 Abdominal fat content
2.6 Effect of dietary variation and feed restriction on skeletal
deformities
2.7 Effect of dietary variation and feed restriction on Economics
2.1 Compensatory growth in the broiler chicken
Compensatory growth is defined as abnormally rapid growth
relative to age within a breed of animal (Wilson and Osbourn, 1960). Un
interrupted growth of animals follows a predetermined growth curve.
Temporary conditions unfavourable for growth, such as under nutrition
or illness, make the animal deviate from its original growth path. When
favourable conditions are restored, the animal often exhibits accelerated
growth. In animal production, most classical studies in compensatory
growth have involved sheep and cattle (O’Donovan, 1984).
Two hypotheses have been put forward to explain the mechanisms
that govern compensatory growth. The first is the ‘central control’
hypothesis, which suggests that the body has a set point for body size
appropriate for a particular age and that this control mechanism resides
in the central nervous system (Wilson and Osbourn, 1960). After a period
of under nutrition, the body tries to attain size that is appropriate for age
in the shortest possible time. The second is the ‘peripheral control’
hypotheses, which suggests that control of body size is determined by the
tissues where cell number or, more accurately, DNA determines the
extent of growth following a period of under nutrition or illness (Pitts,
1986).
A schematic representation of different growth curves of broiler
chickens as described by Leeson and Summers (1991) is given in Fig. 1.
Lines A, B and C represent three potential growth curves of broilers that
reach approximately 2 kg body weight at 42 days of age. If birds grow at
a uniform rate, growth will be as depicted by line B and represents
perhaps a biological ideal as far as minimizing stress is concerned
i.e., continual steady growth with no major period of slow or rapid
growth. However, few animals grow with such ‘statistical’ precision. Birds
which grow through lines A and C both reach 2 kg weight at 42 days, yet
Fig. 1: Schematic representation of growth curves of broiler chickens
(Leeson and Summers, 1991)
A: More rapid initial growth and subsequently slower growth approaching market weight
B: Continual steady growth with no slow or rapid growth
C: Initially slower rate of growth, followed by an accelerated growth towards market weight
the routes they take are quite dissimilar. Bird A has more rapid initial
growth and subsequently, a slower growth approaching market weight.
Bird C initially has a slower rate of growth, followed by an accelerated
growth towards market weight.
Bird C will probably exhibit a superior feed conversion because it
will have a lower maintenance requirement especially at early age. The
reason for this reduced maintenance requirement is that, at any specific
age, before reaching point X, the bird has a smaller body mass to
maintain and so will need less feed nutrients for this purpose. Smaller
birds have proportionately higher maintenance requirements, but if C is
sufficiently different from A, there will be a reduction in the absolute
quantity of nutrients going towards maintenance. Totaling these reduced
maintenance needs, while still achieving the desired body weight X
(Fig. 1), must result in more feed directed to growth and so improved feed
efficiency. Nevertheless, this theory should assume that the carcass
composition is unaltered.
Early studies of feed restriction programmes in broilers have been
primarily concerned with lowering body fat and improving the feed
efficiency (Fisher, 1984), which in many cases were attained at the
expense of final body weight. Osbourn and Wilson (1960) and Auckland
and Morris (1971) demonstrated the feasibility of compensatory growth
with chickens and turkeys subjected to feed restriction during early life
so that final body weight is not compromised. Other workers, however,
failed to show complete growth compensation under similar nutritional
regimen (Jones and Farrell, 1992: Zubair and Leeson, 1996b). The
variability in results of studies is obviously due to a number of factors
that influence the response of broiler chickens to a short-term or
prolonged under nutrition.
2.2 Factors that influence compensatory growth
Factors that influence the ability of animals to exhibit
compensatory growth during the period of re-alimentation following
nutritional deprivation were identified by Osbourn and Wilson (1960).
These factors include the nature, severity and duration of under-
nutrition as well as the age at the commencement of under-nutrition and
the degree and pattern of re-alimentation.
2.2.1 Duration and timing of restricted nutrition
Many studies have shown that the longer the period of under-
nutrition, the more difficult it is for broilers to compensate for the
reduction in weight gain (Yu and Robinson, 1992). Feed restriction for a
period of six days allowed for complete body weight recovery, while
recovery was not seen when restriction was more prolonged at 12 days
(Plavnik et al., 1986). Most workers recommended feed restriction of not
more than seven and five days for male and female broilers, respectively,
to allow for full body weight recovery (McMurtry et al., 1988: Plavnik and
Hurwitz, 1991: Shariatmadari and Hosseni, 2001).
Mollison et al. (1984) restricted the feed intake of birds to 90 per
cent of that of control birds from 7 to 49 days of age and reported a
significantly lower final body weight at 56 days of age. The lack of
recovery in body weight by the restricted birds was likely to have been
caused by the prolonged period of restriction, giving no time for the birds
to exhibit complete growth compensation. On the other hand, a feed
restriction period of four days for female broilers allowed for full recovery
in a much shorter time (Jones and Farrell, 1992: Lippens et al., 2000). It
is not clear whether milder restriction programmes of shorter duration
would have any effect on reducing body fat deposition, which is one of
the primary objectives of feed restriction.
Initiation of 6 days feed restriction at any age between 3 and 11
days of age seems to permit complete body weight recovery by 8 weeks of
age in male broilers (Plavnik and Hurwitz, 1988). Similarly, other workers
have recommended the commencement of restriction at 5 to 7 days of
age (Rosebrough et al., 1986). On the other hand Washburn and Bondari
(1978) initiated their feed restriction programme at 3 weeks of age, and
reported very little evidence of compensatory growth, probably because
very little time was allowed for recovery.
2.2.2 Nature and severity of restricted nutrition
The level of restriction imposed is usually calculated to meet the
maintenance energy requirement of the birds, based on the
recommendations of Plavnik and Hurwitz (1989). These workers
estimated the metabolizable energy (ME) requirement for maintenance of
male broilers to be 6.3 KJ/kg W0.67. More severe restriction tends to
compromise the ability of the bird to recovery. The level of feed restriction
which estimated just to meet maintenance energy requirements is
equivalent to about 167 KJ ME/bird/day in the 6 to 12 day period
(approximately 35% of normal intake). This maintenance energy level,
however, must have been over estimated because the feed restricted
birds gained 2 to 4 g body weight each day during the restriction period.
It is also possible, as suggested by some workers, that the birds, even
though in negative energy balance were able to gain weight due to
change in body composition i.e., used fat reserve and deposited more
lean tissue (Lesson et al., 1991: Yu and Robinson, 1992: Zhong et al.,
1995). However, other workers were unable to demonstrate complete
compensatory growth of boilers, which had been subjected to similar
degrees of feed restriction (Plavnik et al., 1986: Robinson et al., 1992).
Later studies by Plavnik and Hurwitz (1991) showed that milder
restriction, which allowed 60 to 70 per cent of normal growth, permits
more realistic recovery.
2.2.3 Condition of re-alimentation
There is at present very limited information about energy and
protein requirements during the re-feeding period. Plavnik and Hurwitz
(1989) re-evaluated the amino acid requirements of broilers during re-
alimentation. Based on the expected growth rate and body composition,
their model calculations showed higher requirements for most of the
essential amino acids, especially during the first two weeks of re-feeding.
Jones and Farrell (1992) demonstrated that dietary
supplementation with lysine and/or methionine during the re-feeding
period resulted in higher final body weight and leaner carcasses. More
consistent results of compensatory growth have been obtained in studies
that have extended the growth period to 7 weeks or more (Upendra
kumar et al., 1997; Nirmala et al., 2005).
2.2.4 Genetic factors
Male broilers have a greater ability to exhibit compensatory growth
following a period of under nutrition than females (McMurty et al., 1988;
Plavnik and Hurwitz, 1991). The results of studies by Plavnik and
Hurwitz (1990) showed that males were able to exhibit complete
compensatory growth when subjected to similar conditions but not
females. The lack of consistency in the response of broilers to early under
nutrition programmes has been attributed by many workers to
differences in strains of birds used (Yu et al., 1990). Cherry et al. (1978)
showed that fast growing broiler strain exhibit little compensatory growth
when compared with slower growing strains. Alsobayel et al. (1989) and
Attia et al. (1998) reported broiler females had higher abdominal fat than
males when subjected to early feed restriction.
Diet dilution resulted in a significant reduction in body weight at
11 days of age in broilers, although by 42 days there was complete
recovery of body weight with no change in overall efficiency of feed
utilisation in both sexes (Leeson et al., 1991).
Saleh et al. (1996) subjected the broilers to feed restriction by 20,
30 or 40 per cent of the fully fed group on day 8, 9, 12 and 13 followed
by ad libitum feeding showed males had higher final body weight than
females.
The feed restriction either in male, female or combined sex broilers
during 2nd and 3rd week of age by 10, 20 and 30 per cent to that of ad
libitum control feeding showed the male broilers attained early
compensatory growth compared to females (Nirmala et al., 2005).
2.2.5 Adipose development and fat deposition
Studies suggesting that fatness at an early age may affect adiposity
at adulthood led to the initiation of studies intended to elucidate whether
nutrition at an early age might have subsequent inductive effects (Nir et
al., 1988). Nutritional studies have indicated that the ages at which the
different processes involved in adiposity (hyperplasia and hypertrophy)
occur can be altered by level of feeding, especially at early ages (Fontana
et al., 1993). Feed restriction treatments are, therefore, mostly imposed
during the second to third week of age in broiler chickens, as an attempt
to alter hyperplastic growth of adipocytes which, at this age, accounts for
most of the growth of the adipose tissue. It is hypothesized that this will
suppress or delay adipocyte proliferation, and this is expected to be
accompanied by lower adiposity in older broilers.
The application of early under nutrition to reduce carcass fat
content in the broiler chickens has met with varying degrees of success.
Reduction in body fat and abdominal fat as a result of early feed
restriction was achieved by a number of workers (Plavnik and Hurwitz,
1985; Nirmala et al., 2005), although a comparable number of studies
showed no real effect (Summers et al., 1990; Zubair and Leeson, 1996b).
Results of number of studies showed that, even though growth of adipose
tissue is controlled during feed restriction, adipose tissue is, however,
capable of hyperplasia during re-feeding. Such adipocyte hyperplasia
continues until the cell number appropriate for the body mass is attained
(Zubair and Leeson, 1996b). A very strong positive relationship has been
reported between development of body mass and adipocyte hyperplasia
in broilers (Cartwright, 1991). These workers suggested that adipose
tissues from larger birds are hypoplastic relative to tissues from birds of
smaller body size.
2.3 Methods of feed restriction
2.3.1 Physical feed restriction
Various methods of under nutrition have been used to retard or
even stop growth during the under nutrition period. The most commonly
used method of feed restriction is simple physical restriction, which
provides a calculated quantity of feed per bird, this often being just
enough to provide for maintenance requirement. This method of feed
restriction has the disadvantage of requiring frequent weighing of feed.
There is the additional problem of feeder space, which if limiting, leads to
non-uniform distribution of the small feed supply, thereby causing
uneven body weight distribution within a flock. Many workers have used
physical methods of feed restriction because birds can adapt to the
feeding of high fibre diets. Such adaptation enables them to digest, to
some extent, the otherwise indigestible fibre, thereby getting more energy
(and possibly other nutrients) than is required to achieve the desired
growth retardation during the under nutrition period. Leeson et al.,
(1991) reported more than expected growth for broilers fed a diet
containing 55 per cent rice hulls, based on the calculated expected
nutrient intake. They suggested that the ingredients used for diet
dilution, such as rice and oat hulls, are assumed to contain little
digestible energy, but may actually provide substantial amounts of
nutrients. Such a situation will obviously interfere with the total energy
intake of the birds during under nutrition, there by changing the growth
pattern.
2.3.2 Diet dilution and chemical methods of feed restriction
While physical feed restriction is the most common technique used
to achieve under nutrition, in practical situations it is very difficult to
distribute feed evenly. With physical feed restriction programmes there is
also the problem of even distribution of micro-nutrients and anti-
coccidial chemicals among the birds in a flock. An alternative system of
achieving uniform under nutrition within a flock is by diet dilution or the
use of other chemical means to restrict intake of specific nutrients or
feed.
Leeson et al. (1991) replaced 25 to 55 per cent of conventional
broiler starter diet with rice hulls during a period of 7 to 16 days and
showed recovery of body weight by 42 days of age. In this study, vitamin
and mineral sources were not affected by the diet dilution.
Jones and Farrell (1992) who fed diets diluted up to 65 per cent
with rice hulls and also obtained growth compensation relative to the
control birds at 48 days of age.
Restriction of feed intake of broilers by chemical means was
suggested by Fancher and Jensen (1988) as an alternative to diet
dilution. These authors used glycolic acid which is naturally occurring
compound in many foods and has been reported to depress feed intake in
a dose dependent manner in broiler chicks. Pinachasov and Jensen
(1989) used glycolic acid as a chemical means of restricting feed intake of
broilers, and compared this with the traditional feed restriction method.
During the restriction period (7-14 days) the feed intake of birds, given
diets supplemented with 1.5 per cent and 3 per cent glycolic acid was
depressed by 17 per cent and 45 per cent, respectively. These reductions
of feed intake due to glycolic acid supplementation resulted in growth
retardation during the under nutrition period to 71 per cent and 41 per
cent respectively, relative to the growth of control birds. Male broilers
exhibited complete body weight recovery at 49 days of age, with no
difference between the birds restricted by the dietary glycolic acid
addition or those subjected to physical feed restriction. Due to its natural
occurrence, glycolic acid may serve as a safe and useful anorectic
compound for restricting feed intake in poultry (Harris and Richardson,
1980). This method of feed restriction has the advantage of ensuring even
distribution of the feed and giving the birds appropriate intake of micro-
ingredients such as anti-coccidials.
2.3.3 Use of low protein or low energy diets
Achieving growth retardation by under nutrition may require extra
labour or mechanization to apply physical feed restriction or the use of
non-digestible materials to dilute the feed. An alternative method of
retarding early growth is the restriction of intake of specific nutrients,
such as protein (Moran, 1979). Broilers require 220, 200 and 180 g/kg
dietary crude protein during the starting, growing and finishing periods,
respectively for optimal growth (NRC, 1994). They tend to increase their
feed intake to make up for deficiencies when fed with diets that are
marginally deficient in crude protein (Fisher, 1984). However, feed intake
is depressed by feeding diets that are severely deficient in crude protein
(Plavnik and Hurwitz, 1990; Michel Picard et al., 1999).
Studies by Plavnik and Hurwitz (1990) showed that ad libitum
feeding of a diet containing only 94 g/kg crude protein from 8 to 14 days
decreased the feed intake of broilers by some 57 per cent. This decrease
in feed intake resulted in 41 per cent growth retardation, which was not
recovered after six weeks of re-alimentation. Deaton et al. (1973) utilized
a low energy diet to reduce body weight of broilers by four weeks of age.
By eight weeks of age males fed a high-energy diet were able to
compensate for the weight loss occurring during the preliminary feeding
of low energy diets. Females required less energy to recover from the lost
body weight than did males.
Calvert et al. (1987) used two levels of diet ME (13.0 and 14.2
MJ/kg) during an under-nutrition period 6 to 12 days of age and fed
birds 167 KJ ME/bird/day. All growth retarded birds observed complete
growth compensation by 56 day of age.
2.4 Effect of dietary variation and feed restriction on performance
Variation in nutrient profile and early feed restriction have been
reported to influence the body weight, feed consumption, feed conversion
ratio and livability of birds which are reviewed as under.
2.4.1 Body weight
Deaton et al. (1973) demonstrated that broilers fed a diet
containing 3141 Kcal of ME/kg (0-4 weeks) had a four per cent reduction
in body weight at four weeks of age as compared to birds fed a diet
containing 3306 Kcal for ME/kg. By eight weeks of age, the birds were
able to compensate for the four per cent reduction in 4th week body
weight, when fed a high energy diet containing 3372 Kcal of ME/kg from
five to eight weeks.
Washburn and Bondari (1978) studied the effects of timing
(duration of 1, 2, 3 and 5 weeks between the ages of 3 to 8 weeks) and
duration (3 to 5 weeks) of skip-a-day restricted feeding on compensatory
growth of broilers and reported a significant (P<0.05) reduction in eight
week body weight of males but not in females in comparison to control
groups.
Broilers fed low level of protein (20%) during growing phase (2 to 5
weeks) exhibited reduced body weight than high protein (24%) and inter
mediate protein (22%) fed groups. By 7 weeks of age, compensatory
growth of those groups that had previously experienced poor
performance was recorded when common finishing rations were fed
(Moran, 1979).
Hargis and Creger (1980) studied the effects of varying dietary
protein and energy levels on growth rate and reported that high dietary
protein levels were detrimental to growth during the starting period (0-14
days), but beneficial in maximizing weight gain during the finishing
period (28-49 days).
Body weight of broilers on quantitative feed restriction at levels of
95, 90 and 85 per cent of adlibitum for two weeks (6-8 weeks) and three
weeks (6-9 weeks of age) were not significantly different from those fed ad
libitum at slaughter at the end of tenth week. However, the birds kept on
restricted diets for four weeks on all levels of restriction showed lower live
weights at slaughter time as compared to those fed ad lib (Sunaria and
Sharda, 1981).
Restriction of feed intake in broilers to 90 per cent of ad libitum
intake in early life significantly (P<0.01) reduced the 49th day body weight
(Mollison et al., 1984).
Plavnik and Hurwitz (1985) studied the performance of broiler
chicks due to feed restriction by way of providing energy from 30 to 45
Kcal per day for different periods ranging from 6 to 28 days started at the
age of one week and found that the body weight gain in feed restricted
birds was lowered during the first two weeks of refeeding but later
exceeded that of control.
The effects of early nutrition alternations upon market age broiler
performance was demonstrated by Bryan and Leo (1986) and observed
that chicks fed diets containing 2850 Kcal ME/kg with either 18, 23 or
28 per cent crude protein for the first week, did not differ significantly in
the 7th week body weight among treatments.
The initiation of six days feed restriction at any age between 3 and
11 days of age seems to permit complete body weight recovery by eight
weeks of age in male broilers (Plavnik and Hurwitz, 1988).
Victoria et al. (1988), found that ad libitum fed broilers were at
least 41 per cent heavier throughout the trial period compared to those
on the 25 per cent restricted diet during 5 to 39 days of age.
Feed restriction in broilers by 76 and 85 per cent or 69 and 75 per
cent of ad libitum at second and third weeks followed by ad libitum
feeding until seven to eight weeks of age showed no significant difference
in weight gain between the control and restricted birds (Alsobayel et al.,
1989).
Calvert et al. (1989) studied the effect of three levels of feed intake,
ad libitum, 40 Kcal ME/d from 6 d through 12 d and 40 Kcal ME/d from
6 d through 18 d post-hatching, on weight gain and found that there was
no effect of restriction on weight gains from 21 to 56 days of age.
Oporta and Rubio (1989) found that the body weight of broilers
was not affected when subjected to 20 and 30 per cent feed restriction
during the fourth and fifth week of age. They concluded that it was
possible to restrict feed up to 30 per cent without affecting other
production characteristics.
Feed regimen that restricted the growth of male broilers severely
between 6 and 11 or 6 and 12 days old followed by increase in dietary
nutrient density resulted in an enhanced growth rate (Plavnik and
Hurwitz, 1989).
The effect of different nutrient restriction programs in early life of
broilers was studied by Cabel and Waldroup (1990) and found that the
compensatory gain was not observed consistently in the experiment.
Summers et al. (1990) reported no significant difference in 42 day
body weights between ad libitum fed birds and birds either restricted in
feed intake or fed diluted diets between 7 and 14 days or between ad
libitum fed birds and birds fed higher levels of dietary protein between 36
and 42 days of age.
Yu et al. (1990) studied the growth and body composition of broiler
chickens in response to different regimes of feed restriction (Ad libitum,
skip-a-day, daily or hourly) between 8 and 14 day post hatch and
observed that on day 56, body weight of restricted chicks was not
significantly different from one another, but was significantly less than
that of full-fed birds.
Ballay et al. (1992) studied the initiation and the length of different
feed restriction programs on broilers and reported that chicks restricted
for only 6 days during first 18 days of age reached body weight
equivalent to those of chicks eating ad libitum at 39 days of age, whereas,
chicks fed on restricted feed for more than six days during the first 18
days after hatch were lower in body weight than those of ad libitum fed
chicks.
Fontana et al. (1992) reported that the broilers subjected to 5 or 6
or 7 days of early feed restriction commencing at 4 days of age, had
significantly lower mean final body weight than control for all duration.
Feed regimen which restricted the growth of male broilers by about
58 per cent between 6 and 12 days old followed by adlibitum feeding had
no significant effect on body weight at 47 days of age (Plavnik and
Balnave, 1992).
Robinson et al. (1992) studied the growth performance in full fed
and feed restricted broilers and roaster chicken and reported that the
time taken for attaining the market weight delayed by 2 or 3 days in the
early short term (7 days) feed restricted birds. Also, the optimum timing
for feed restriction was during the second week rather than later.
Feed restriction in broilers by 50 and 65 per cent of ad libitum at 6
to 14 days and 8 to 14 days of age, respectively exhibited compensatory
growth at 21, 35 and 45 days of age equivalent to that of ad libitum fed
groups (Scheideler, 1993).
Broilers fed with reduced nutrient density (175 g protein/kg)
between 7 and 14 day of age, causing a uniform reduction in body weight
of 15 to 16 per cent at 14 day of age, which was fully recouped by
compensatory growth between 15 and 49 days of age (Carter et al.,
1994).
Susbilla et al. (1994) demonstrated that broilers restricted in
intake to 50 or 75 per cent of ad libitum from 5 to 11 days of age showed
higher (P<0.05) relative growth rate from 12 to 39 days of age in 50 per
cent restricted group compared to 75 per cent restricted group and
control group.
Feed restriction by 50 per cent diet dilution with oat hulls for six
days starting at 6 days of age in male broilers showed complete growth
compensation by 35 days of age (Zubair and Leeson, 1994a). Again they
demonstrated that the lower metabolic rate in ‘restricted re-fed’ broilers
does not a part in growth compensation (Zubair and Leeson, 1994b).
Broiler chicks reared from 1 to 56 days of age under feed
restriction from 8 to 56 days of age with 8 hours per day of access to feed
had 11.2 per cent reduction in growth rate when compared to control
(Arce Menocal et al., 1995),
Deaton (1995) conducted a study on feeding of 90, 75 and 60 per
cent of previous 24 hour feed consumption of full fed controls from 7 to
14 days of age or 80 and 60 per cent from 8 to 16 days of age and
concluded that the body weight of broilers equated the control at 41 days
of age in 90 per cent feed restriction.
The effects of feed restriction was studied by Santoso et al. (1995)
by way of providing 50 per cent of ad libitum for 5, 10 and 15 days
starting from 5 days old followed by ad libitum up to 56 day old and
reported that body weight of broiler chickens fed 50 per cent ad libitum
for 10 and 15 days had significantly lower body weight than those of ad
libitum fed chickens.
Zhong et al. (1995) found that feed restriction of 1.49 Kcal/g body
weight2/3 daily from 7 to 12 days of age showed no difference in mean
body weight between the full fed and restricted males and combined sex
broilers at 49 days of age.
A broiler experiment was conducted by Ramlah et al. (1996) by
way of providing feed ad libitum, restricted to 75 per cent of ad libitum
intake from 8 to 14 days old or restricted to 50 per cent of ad libitum
intake from 15 to 21 days old and concluded no compensatory gain in
restricted groups.
Saleh et al. (1996) subjected the broilers to feed restriction by 20,
30 or 40 per cent of the fully fed group on Day 8, 9, 12 and 13 followed
by ad libitum feeding. They concluded that final body weight did not differ
among those restricted to 20 or 40 per cent and those fully fed.
The effect of early life feed restriction in male broilers was
demonstrated by Zubair and Leeson (1996b) by way of providing 50 per
cent physical feed restriction during the period of 6 to 12 days of age
followed by gradual refeeding until 42 days of age and reported that
complete compensatory growth was not achieved by 42 days by feed
restricted birds relative to control.
The effect of different restricted feeding programmes was studied
by Cristofori et al. (1997) and they concluded that feed restricted chicken
had a good but not complete compensatory growth when compared with
the control.
Qualitative feed restriction by diluting the diet with 0, 20, 40 and
60 per cent of rice hulls between 7 and 14 days of age in broilers, had
significantly (P<0.05) reduced the body weight and weight gain at 15
days of age as compared to the control. However, there was complete
recovery in body weight by 42 days of age (Upendrakumar et al., 1997).
Attia et al. (1998) studied the effect of broilers subjected to feed
restriction during 2nd week by 50 per cent of feed consumed by ad libitum
controls or 50 per cent of ad libitum during 2nd and 3rd week of age and
reported that body weight of one week restricted chickens did not differ
from those of controls whereas, two weeks restricted chickens showed
the lowest body weight at 7 weeks of age.
Benyi and Habi Habi (1998) conducted an experiment consisted of
broiler chicks fed with 85 or 70 per cent of ad libitum or ad libitum for 5
days per week with 3rd and 5th days of food withdrawal for 28 days and
reported a significantly reduced final body weight and rate of growth in
quantitative feed restriction to 85 and 70 per cent of ad libitum and
reduction in feeding time by two days per week.
Diets diluted with 50 and 20 per cent wheat bran between 0 to 5
days and 5 to 11 days of age, respectively followed by control diet showed
lower body weight in restricted broilers compared to control at 41 day of
age (Michel Picard et al., 1999).
Vargas et al. (1999) studied four levels of quantitative feed
restriction (0, 15, 30 and 45%) and two periods (from 8 to 14 and from 8
to 17 days of age) in broilers and reported that the body weight and
weight gain reduced in higher levels of feed restriction.
Lippens et al. (2000) restricted the feed to broilers to 80 or 90 per
cent of ad libitum feed intake for 4 days or 80 per cent for 8 days started
from 4th day of age followed by adlibitum feeding and observed that the
final body weight in broilers kept on 90 per cent of adlibitum intake for 4
days did not differ significantly but lower than that of controls.
The effects of early life under nutrition in broilers was studied by
Lee and Leeson (2001) by providing 0.75 Kcal ME/g b.wt.0.67 for 4 days,
1.5 Kcal ME/g b.wt.0.67 for 5 days or 2.25 Kcal ME/g b.wt.0.67 for 6 days
started from 6th day of age and found that restricted birds were smaller
following feed restriction although growth compensation occurred and at
49 days all restricted birds were heavier than full fed control birds.
Shariatmadari and Hosseni (2001) studied the effects of feed
restriction during the early stage of growth (7 to 14 days) and later period
(42 to 49 days), with three levels of restriction (90, 80 and 70%) on
broiler performance and found that the birds on feed restriction at the
beginning of the growth period (7-14 days) took 2.5 days longer to reach
the same body weight as the control group. The birds on late restriction
(42 to 49 days) reached this weight 3.5 days later.
The effects of energy and protein dilution (adding rice hulls at 0,
100, 150, 200, 250 and 300 g/kg) between 6 and 12 days of age in
broilers was demonstrated by Yussefi Kelaricolaii et al. (2001) and they
found that diet dilution reduced the weight gains between Day 6 and 12.
Due to compensatory growth, no significant differences between
treatments were observed at 42 days of age.
Lippens et al. (2002) reported broilers restricted to 80 per cent of
the ad libitum intake of the previous 24 hours of the control group from
Day 4 to 7. After the period of restriction all birds were fed ad libitum up
to 42 days of age and found that compensatory growth was substantial.
They were also concluded that a retardation of the early growth of fast
growing broiler chickens can, in certain circumstances increases
performance and nitrogen retention.
Santoso (2002) studied the effect of early feed restriction by
providing 25 per cent of ad libitum for 4 to 6 days, 50 per cent of ad
libitum for 4 to 6 days and 75 per cent of ad libitum for 4 to 6 days and
reported that restricted broilers exhibited compensatory growth and the
level of feed restriction significantly influenced the body weight but
duration of feed restriction had no effect.
Broilers restricted to 90 per cent of ad libitum intake of control
group during different intervals showed non-significant differences
across treatments in the body weight at 42 days of age (Urdaneta Rincon
and Leeson, 2002).
Camacho et al. (2004) carried out an experiment by restricting feed
to the broilers for 8 hours/day for 14 days at 21 or 28, 14 or 21 and 7 or
14 day of age and concluded that the quantitative feed restriction at 7
day of age was permitted compensatory growth sufficient to equal the
production characteristics of the control group at 49 day of age.
The effect of meal time feeding (food was withdrawn from 9 am to 3
pm) and low protein diet (19.5% protein) feeding from 7 to 21 days of age
in broilers was studied by Konca et al. (2004) and they found that
compensatory growth at 45 days of age was not observed either for meal
time fed broilers or low protein fed broilers from 7 to 21 days.
Shariatmadari and Vaeztorshizi (2004) studied the effect of three
feeding levels (control, 15% and 30% below ad libitum) from 7 to 14 days
of age on male and female broilers performance and observed that male
broilers had better compensatory growth ability as judged by significantly
(P<0.05) higher growth rates than females.
Broiler chicks subjected to ad libitum feed from 7 to 13 days of age
or given 25 and 50 per cent of ad libitum intake on a daily basis (physical
restriction) or 100 per cent of ad libitum intake on a daily basis, when the
diets were diluted with 25 and 50 per cent rice hulls (dilution restriction)
showed physically restricted birds gained significantly more weight than
their diet diluted counterparts. Birds in all of the restricted groups
gained weight similar to the full fed birds at 49 day of age (Toghiani et
al., 2004).
The feed restriction either in male, female or combined sex broilers
during second and third week of age by 10, 20 and 30 per cent to that of
ad libitum control feeding did not affect the final 7th week body weight
between treatments (Nirmala et al., 2005).
2.4.2 Feed consumption and feed conversion ratio
Washburn and Bondari (1978) studied the effects of timing
(duration of 1, 2, 3, 4 and 5 weeks between the ages of 3 to 8 weeks) and
duration (3 to 5 weeks) of skip-a-day restricted feeding and reported a
reduction of as much as 10 per cent feed consumption and higher feed
conversion ratio (FCR) in all restricted groups than the control.
Broiler fed lowest level of protein (20%) during growing period (2 to
5 weeks) exhibited poorer utilization of feed than high protein (24%) and
intermediate protein (22%) fed groups. By 7 weeks of age, groups which
had received the lowest protein and exhibited the poorest feed conversion
(between 2-5 weeks), now made the best use of their feed when common
finishing rations (5-7 weeks) were fed (Moran, 1979).
The effects of varying dietary protein and energy levels on growth
rate was studied by Hargis and Creger (1980) and reported that high
dietary protein levels were detrimental to growth during the starting
period (0-14 days) but beneficial in maximising feed efficiency during the
finishing period (28 to 49 days).
Starrjackson et al. (1982) reported broilers fed varying levels of
dietary protein (16, 20, 24, 28, 32 and 36%) and energy (2600, 2800,
3000, 3200, 3400 and 3600 Kcal ME/kg) to determine the effect of
alteration in nutrient density on performance and observed that feed
efficiency improved with increased dietary protein or energy.
Restriction of feed intake to 90 per cent of ad libitum intake in
early life of broilers had significantly improved the feed intake compared
to groups fed ad libitum diet (Mollison et al., 1984).
Plavnik and Hurwitz (1985) studied the performance of broiler
chicks due to feed restriction by way of providing energy from 30 to 45
Kcal per day for different periods ranging from 6 to 28 days started at the
age of one week and found that cumulative feed efficiency was improved
over the control.
The effect of age, duration and sex on early feed restriction in
broiler chicks was demonstrated by Plavnik and Hurwitz (1988) and
found that early feed restriction in males for seven days resulted in
improved feed efficiency on age basis or on body weight basis after body
weight has reached 0.7 to 1.0 kg, but with females little benefit in feed
efficiency when compared with ad libitum fed birds on body weight basis.
Victoria et al. (1988) found that feed efficiency was better in the ad
libitum fed group up to 11 days of age and then became similar to those
on the 25 per cent restricted diet during 5 to 39 days of age.
Calvert et al. (1989) studied the effect of three levels of feed intake:
ad libitum, 40 Kcal ME/day from 6 through 12 day and 40 Kcal ME/day
from 6 through 18 day posthatching and found that feed: gain improved
(P<0.05) in both restricted groups.
Feed intake (5005, 5002 and 5004 g) and feed efficiency (0.451,
0.430 and 0.455) in broilers were not affected by feed restriction (ad
libitum 20% and 30%) during 4th and 5th week (Oporta and Rubio, 1989).
Feed regimen, which affects the feed efficiency of male broilers
between 6 and 11 or 6 & 12 days old followed by increase in nutrient
density resulted in an improved feed efficiency (Plavnik and Hurwitz,
1989).
Shyamsunder et al. (1989) studied the performance of broilers fed
continuously 17 or 19 per cent protein diet for 8 weeks or birds fed 17 or
19 per cent protein diet for 3, 4 and 5 weeks and reported cumulative
feed intake in all restricted group was similar to that of control group.
The feed efficiency of birds maintained on restriction for 3 to 5 weeks was
comparable to those fed control diet, but the groups kept continuously
on 17 or 19 per cent protein diet for 8 weeks had significantly poor feed
conversion efficiency than the control group.
Cabel and Waldroup (1990) studied the effect of different nutrient
restriction programmes in early life of broilers and they reported a
general improvement in feed efficiency by nutrient restriction.
Low-sodium, low-protein or a control diet fed ad libitum to 8-day-
old male broiler chickens for 6 days showed lowest weight gain in low
protein diet feed groups and did not recover at 56 days old, however feed
efficiency was improved significantly (Plavnik and Hurwitz, 1990).
Summers et al. (1990) reported no significant difference in feed:
gain ratios was noticed between ad libitum fed birds and birds either
restricted in feed intake or fed diluted diets between 7 and 14 days or
between ad libitum fed birds and birds fed higher levels of dietary protein
between 36 and 42 days of age.
Attia et al. (1991) conducted a study on broilers subjected to ad
libitum feeding or feed restriction to 50 per cent of control feed intake
between 1 and 3 weeks or given 20 per cent dried chicken excreta during
5 and 6 weeks old and found that cumulative FCR for control and feed
restricted birds were the same.
Leeson et al. (1991) used conventional starter diets, which had
been diluted with 25, 40 or 55 per cent rice hulls from 7 to 16 days of
age and reported no change in overall feed efficiency.
Skip-a-day feed restriction programmes during the starting period
in broilers can effectively reduced the incidence of ascites syndrome
without severely compromising body weight gain or feed conversion (Arce
et al., 1992).
Ballay et al. (1992) studied the initiation and the length of different
feed restriction programs on broilers and reported that chicks restricted
for the whole experiment had superior feed efficiency with low body
weights.
A broiler experiment was carried out by Fontana et al. (1992) by
providing 40 Kcal of ME/bird/day, commencing at 4 days of age for the
duration of 5, 6 or 7 days and found that feed conversion ratio for
restricted broilers were significantly lower at 28 and 49 days of age than
for birds consuming feed ad libitum.
The growth performance in full fed and feed restricted broilers and
roaster chicken was observed by Robinson et al. (1992) and reported that
the feed efficiency was not affected by short term feed restriction.
A period of short term feed restriction and subsequent refeeding in
broiler chickens is sometimes, but not always, marked by catch-up
growth and it is accompanied by a corresponding increase in feed intake
(Yu and Robinson, 1992).
Roth et al. (1993) studied the feed restriction in broilers at 5 days
old to 50, 60 or 70 per cent of free intake for 2 weeks, 70 per cent for 2, 3
and 4 weeks and at 65 per cent of free intake for 4 or 12 days and
concluded that increasing the duration of feed restriction decrease the
cumulative feed conversion ratio.
Dietary restriction in broiler chickens (175 g protein/kg between 7
and 14 day of age) caused a uniform reduction in body weight at 14 days
of age, which was fully recouped by compensatory growth on day 49.
However, food intake was not significantly affected (Carter et al., 1994).
Susbilla et al. (1994) reported non-significant difference among
different groups in feed conversion ratio of broilers restricted to 50 or 75
per cent of ad libitum intake for 5 to 11 days of age.
Feed restriction by 50 per cent diet dilution with oat hulls for
six days starting at 6 days of age showed superior feed efficiency
(P<0.05) in feed restricted male broilers relative to control birds
(Zubair and Leeson, 1994a).
Deaton (1995) conducted a study in broilers on feeding of 90, 75
and 60 per cent of previous 24 hour feed consumption of full fed controls
from 7 to 14 days of age or 80 and 60 per cent from 8 to 16 days of age
and concluded that early feed restriction improved the feed conversion
ratio.
Broilers subjected to varying dietary protein levels (20 and 22% CP)
and restricted feeding (0,10 & 20%) showed 20 per cent CP fed groups
and 10 per cent feed restriction groups had superior feed efficiency than
that of control (Hirwade et al., 1995).
Santoso et al. (1995) studied the effects of feed restriction by way
of providing 50 per cent ad libitum for 5, 10 and 15 days starting from 5
days old followed by ad libitum feeding up to 56 days old and reported a
better feed conversion ratio in broiler chicks fed 50 per cent ad libitum for
10 and 15 days than those of ad libitum fed birds.
Zhong et al. (1995) reported feed conversion was better (P<0.05) for
restricted broilers than full fed broilers.
A broiler experiment was conducted by Ramlah et al. (1996), which
consisted of providing feed ad libitum, restricted to 75 per cent of ad
libitum intake from 8 to 14 days of age and restricted to 50 per cent of ad
libitum intake from 15 to 21 days of age and they observed that the feed
conversion efficiency was generally improved by feed restriction.
Saleh et al. (1996) conducted a study on broilers subjected to feed
restriction by 20, 30 or 40 per cent of the fully fed group on day 8, 9, 12
and 13 followed by ad libitum feeding and reported an initial
improvement in feed conversion ratio, but insignificant final values in
restricted feeding when compared with control group.
The effect of early life feed restriction in male broilers was studied
by Zubair and Leeson (1996b) by way of providing 50 per cent physical
feed restriction during the period of 6 to 12 days of age followed by
gradual refeeding until 42 days of age and reported consistent
improvement in feed efficiency among treatment groups.
Upendra Kumar et al. (1997) studied the effects of diets diluted
with 0, 20, 40 and 60 per cent of rice hulls between 7 and 14 days of age
in broilers and concluded that overall feed intake was significantly
increased with increase in diet dilution with no change in overall feed
efficiency.
Broilers subjected to 50 per cent of ad libitum feed intake on daily
basis from 6 to 11 days of age were more efficient in overall energy
intake: body weight gain (P<0.01) (Leeson and Zubair, 1997).
Attia et al. (1998) studied the effect of broilers subjected to feed
restriction during 2nd week by 50 per cent of feed consumed by ad libitum
controls or 50 per cent of ad libitum during 2nd and 3rd week of age and
reported a better feed to gain ratio in two weeks feed restricted chickens
than that of controls at 7 weeks of age.
Low feed intake was recorded in broilers fed with low nutrient
density diet (16% CP, 2800 Kcal ME/kg) between 0 to 70 days of age.
Feed efficiency was poorer in the starter period. However, after this time,
feed efficiency for this group normalized and these birds had the
numerically lowest efficiency in the 49 to 70 day finisher period when
compared to high density diet fed groups (Leeson et al., 1999).
Vargas et al. (1999) studied four levels of feed restriction (0, 15, 30
and 45%) and two periods (8 to 14 and 8 to 17 days of age) in broilers
and reported a improved feed : gain ratio in feed restricted groups.
Broilers restricted to 80 or 90 per cent of ad libitum feed intake for
4 days or 80 per cent for 8 days starting from 4th day of age followed by
ad libitum feeding revealed no significant differences in feed conversion
among treatment groups (Lippens et al., 2000).
Lee and Leeson (2001) studied the effects of early life under
nutrient in broilers by providing 0.75 Kcal ME/g BW0.75 for days, 1.5
Kcal ME/g BW0.75 for 6 days starting from 6th day of age and found an
improved feed conversion in restricted birds than full-fed control birds.
The effects of feed restriction (90, 80 and 70 per cent of ad libitum
intake) during the early stage of growth (7-14 days) and later period (42-
49 days) in broilers was studied by Shariatmadari and Hosseni (2001)
and they found that the feed conversion efficiency of the birds given the
early feed restriction was better than the control group when considered
at the same age and on the same body weight basis. Birds restricted at
the late stage of their growth not only had a better feed conversion
efficiency at the same age as the control group, but had a better feed
conversion efficiency on the same weight basis.
The effects of energy and protein dilution (adding rice hulls at 0,
100, 150, 200, 250 and 300 g/kg) between 6 and 12 days of age in
broilers was demonstrated by Yussefikelari Colaii et al. (2001) and they
observed that feed intake following the feed restriction period tended to
be less (P>0.05) for the birds that received the diluted diets as compared
to control and diet dilution had no significant effect on feed conversion
ratio.
Santoso (2002) studied the effect of early feed restriction by
providing 25 per cent of ad libitum for 4 to 6 days, 50 per cent of ad
libitum for 4 to 6 days and 75 per cent of ad libitum for 4 to 6 days, and
reported a higher feed conversion ratio than the control.
Broilers restricted to 90 per cent of ad libitum intake of control
group during different intervals showed significant linear improvement in
feed conversion ratio at 42 days (Urdaneta Rincon and Leeson, 2002).
The effect of mealtime feeding (food was withdrawn from 9 am to 3
pm) and low protein diet feeding (19.5% protein) from 7 to 12 days of age
in broilers was studied by Konca et al. (2004) and found that feed intake
was reduced by mealtime feeding. However, better-feed conversion was
achieved by mealtime feeding.
Shariatmadari and Vaeztorshizi (2004) studied the effect of three
feeding levels (Control, 15% and 30% below ad libitum) from 7 to 14 days
of age on male and female broiler performance and observed that male
broilers had a better-feed efficiency ratio than females.
Broiler chicks subjected to ad libitum feed from 7 to 13 days of age
or given 25 and 50 per cent of ad libitum intake on a daily basis (physical
restriction) or 100 per cent of ad libitum intake on a daily basis, when the
diets were diluted with 25 and 50 per cent rice hulls (dilution restriction)
showed feed intake was increased after restriction period and there was
no difference in the feed conversion after restriction period (13 to 40
days) between different groups (Toghiani et al., 2004).
The feed restriction either in male, female or combined sex broilers
during second and third week of age by 10, 20 and 30 per cent to that of
ad libitum control feeding did not affect the final seventh week
cumulative feed consumption and feed efficiency between treatments
(Nirmala et al., 2005).
2.4.3 Livability of birds
Peter et al. (1972) studied the influence of restricted feed intake on
the response of chickens to Marek’s disease and reported no mortality in
groups restricted to 70 or 60 per cent ad libitum intake prior to 7th week.
Whereas, mortality was seen as early as the 27th day in full fed groups.
The mortality due to ascites in broiler chicks may be reduced when
feed was restricted up to 30 per cent without affecting other production
characteristics (Oporta and Rubio, 1989).
The role of growth of commercial broilers and its relation to the
ascites syndrome was studied by Palos Rodriguez et al. (1991) and
reported restricted feeding (75.0 or 82.5%) up to 28 days of age followed
by ad libitum feeding up to 56 days reduced the ascites mortality without
affecting the final body weight.
Ballay et al. (1992) studied the initiation and the length of different
feed restriction programs on broilers and reported overall mortality was
less in restricted groups.
The control of ascites syndrome by feed restriction techniques was
demonstrated by Arce et al. (1992) and found that skip-a-day feed
restriction programs during the starting period can effectively reduce the
incidence of ascites syndrome without severely compromising body
weight gain or feed conversion.
The mortality of broiler chicks reared from 1 to 56 days of age
under feed restriction from 8 to 56 days of age with 8 hours per day of
access to feed were 88 per cent less when compared to control
(Arcemenocal et al., 1995).
Ramlah et al. (1996) conducted an experiment in broilers (0-42
days) consisted of providing feed ad libitum, restriction to 75 per cent of
ad libitum intake from 8 to 14 days old and restricted to 50 per cent of ad
libitum intake from 15 to 21 days old and concluded that the mortality
rate in the restricted groups was lower than the full fed groups.
Broilers subjected to feed restriction by 20, 30 or 40 per cent of the
fully fed group on day 8, 9, 12 and 13 followed by ad libitum feeding
showed decreased mortality rate in restricted feeding group than the
control group (Saleh et al., 1996).
A significantly lower mortality was recorded in the feed restricted
flocks (12 hours feed/day at 15-35 days of age) than in the fully fed flock
aged from 3 to 7 weeks (Tottori et al., 1997).
The broilers subjected to quantitative feed restriction of 0, 10, 20,
30 and 50 per cent from 8 to 14 days had decreased mortality rate than
the control. Also, birds fed ad libitum had highest sudden death
syndrome (SDS) against feed restricted birds (Gonzales et al., 1998).
The broilers restricted to 80 or 90 per cent of ad libitum feed intake
for 4 days or 80 per cent for 8 days followed by ad libitum feeding
revealed reduction in mortality rate and sudden death syndrome in
restricted groups than the control group (Lippens et al., 2000).
Lippens et al. (2002) in their study, the broilers were restricted to
80 per cent of ad libitum intake of previous 24 hours of the control group
from 4th to 7th day of age followed by ad libitum feeding and concluded
that the retardation of early growth of fast growing broiler chickens could
reduce mortality and increase performance.
The effect of early feed restriction was studied by Santoso (2002) by
providing 25 per cent of ad libitum for 4 to 6 days, 50 per cent of ad
libitum for 4 to 6 days and 75 per cent of ad libitum for 4 to 6 days and
reported inconsistent mortality rate in early feed restricted broiler
groups.
Camacho et al. (2004) carried out an experiment by restricting feed
to the broilers for 8 hours/day for 14 days at 21 or 28 day, 14 or 21 day
and 7 or 14 day of age and concluded that the quantitative feed
restriction at 7 days of age reduced the mortality from ascites.
The feed restriction either in male, female or combined sex broilers
during 2nd and 3rd week of age by 10, 20 and 30 per cent to that of ad
libitum control feeding showed hundred per cent livability in female
broilers up to 7th week of age both in feed restricted groups and in ad
libitum fed control group, such livability was recorded in male and
combined sex broilers up to 5th week of age (Nirmala et al., 2005).
2.5 Effect of dietary variation and feed restriction on carcass characteristics
Dressed carcass percentage tended to increase with increasing
dietary energy level (Farrell et al., 1973).
Moran (1979) reported percentage apparent carcass yield was not
affected when broilers fed with lowest level of protein (20%) during
growing phase (2 to 5 weeks) followed by normal finishing ration (6 to 7
weeks).
Significantly higher dressing percentage was recorded in broilers
subjected to quantitative feed restriction at levels of 95, 90 and 85 per
cent of ad libitum for 2 and 3 weeks as compared to those fed ad libitum
(Sunaria and Sharda, 1981).
The effect of early protein restriction on the meat quality of broilers
was studied by Choudhary and Aggarwal (1986) and found that the per
cent protein content of meat increased with increase in age, however with
a decrease in protein in feed, the per cent protein content of meat also
decreased.
Leeson et al. (1991) used conventional broiler starter diets, which
had been diluted with 25, 40 or 55 per cent ground rice hulls, from 7 to
16 days of age and reported diet dilution had no effect on carcass
characteristics at 42 days of age.
Broilers subjected to either ad libitum access or restricted to
alternate day access to feed initiated at different ages and lasted for
different durations showed feeding regimens had little effect on organ
weights (Ballay et al., 1992).
Fontana et al. (1993) carried out an experiment by restricting the
feed to broilers by providing 40 Kcal of ME/bird/ day, commencing at 4
days of age for the duration of 6 or 7 days and observed that early feed
restriction minimally affects organ weights.
Organ weights taken during realimentation showed significantly
(P<0.05) heavier liver and pancreas for feed restricted broilers (50% of ad
libitum between 6-12 days of age) compared to those fed ad libitum
(Zubair and Leeson, 1994b).
The increased weight of the empty digestive tract may have
contributed to the ability of the broiler chickens to achieve compensatory
growth after the early food restriction period (Susbilla et al., 1994).
Broilers subjected to varying dietary protein levels and restricted
feeding showed higher edible meat per kg live weight in restricted groups
than the control birds (Hirwade et al., 1995).
Palo et al. (1995) reported absolute and relative weights of supply
organs (proventriculus, gizzard, small intestine, liver and pancreas) were
less affected by feed restriction and responded more quickly to refeeding
than the whole body.
The effect of energy and protein restriction on carcass
characteristics of broilers was studied by Ramarao et al. (1996) and
found that dietary regimen had no significant effect on blood and feather
loss and ready-to-cook yields.
Ramlah et al. (1996) concluded that there was no effect on dressing
percentage due to early feed restriction in broilers. But, the weights of
liver and gizzard were affected due to restriction.
Saleh et al. (1996) studied on broilers subjected to feed restriction
by 20, 30 or 40 per cent of the fully fed group on Day 8, 9, 12 and 13
followed by ad libitum feeding and found that the dressing percentage of
most severely restricted groups was higher than that of corresponding
controls.
The effect of different restriction feeding programs was studied by
Cristofori et al. (1997) and they concluded that broilers subjected to feed
restriction by daily amount to satisfy their metabolic requirements in
early stage from 7 to 21 days showed the best carcass visual scores.
Diet dilution with 0, 20, 40 and 60 per cent of rice hulls between 7
and 14 days of age in broilers had no effect on per cent dressed and
eviscerated weight at 56 days of age (Upendrakumar et al., 1997).
The gut development could not be stimulated by diluting the
starter diet with wheat bran during 11 days after hatch in broilers
(Michel Picard et al., 1999).
Vargas et al. (1999) studied four levels of feed restriction in broilers
(0, 15, 30 and 45%) and two periods (from 8 to 14 and from 8 to 17 days
of age) and reported a decrease in total carcass yield and breast yield and
increase in edible viscera up to level of 22.29 per cent in feed restriction.
The broilers restricted to 80 or 90 per cent of ad libitum feed intake
for 4 days or 80 per cent for 8 days followed by ad libitum feeding
revealed 80 per cent of ad libitum intake for 8 days had a significant
lower carcass yield than that of control (Lippens et al., 2000).
The effects of early life under nutrition in broilers was studied by
Lee and Leeson (2001) by feeding 0.75 Kcal ME/g BW0.67 for 4 days, 1.5
Kcal ME/g BW0.67 for 5 days or 2.25 Kcal ME/g BW0.67 for 6 days started
from 6th day of age and they observed decline in carcass yield for birds
fed with 0.75 Kcal ME/g BW0.67 for 4 days. Whereas, superior breast
meat yield was recorded in birds fed with 1.5 Kcal ME/g BW0.67 for 5
days.
Urdaneta Rincon and Leeson (2002) reported broilers restricted to
95, 90 or 85 per cent of ad libitum intake of control group during
different intervals showed ad libitum fed birds had the heaviest carcass
weight and breast meat yields and a progressive reduction in both
parameters was noted with increasing feed restriction.
The effect of three feeding levels (control, 15% and 30% below ad
libitum) during 7 to 14 days of age on male and female broiler
performance was demonstrated by Shariatmadari and Vaeztorshizi
(2004) and they found that feed restriction had no effect on carcass
components and there was no difference between carcass components of
male and females.
Broiler chicks were full fed from 7 to 13 days of age or given 25
and 50 per cent of ad libitum intake on a daily basis (physical restriction)
or 100 per cent of ad libitum intake on a daily basis, when the diets were
diluted with 25 and 50 per cent rice hulls (dilution restriction). The
results showed that method and severity of restriction had no effect on
intestine and liver weight (Toghiani et al., 2004).
The carcass characteristics (pre-slaughter weight, eviscerated
weight, ready-to-cook percentage, giblets weights) at 7th week of age in
male, female and combined sex broilers did not differ significantly due to
feed restriction at early ages (Nirmala et al., 2005).
2.5.1 Abdominal fat content
Restriction of feed intake to 90 per cent of ad libitum intake in
early life had significantly reduced the abdominal fat pad size at 49 days
of age in broilers (Mollison et al., 1984).
Plavnik and Hurwitz (1985) studied the performance of broiler
chicks due to feed restriction by way of providing energy from 30 to 45
Kcal/day for different periods ranging from 6 to 28 days started at the
age of one week and found a reduction in abdominal fat at 8 weeks of age
in early energy restricted groups.
Plavnik and Hurwitz (1988) studied the effect of age, duration and
sex on early feed restriction in broiler chicks and found that feed
restriction reduced the amount of abdominal fat at the age of 54 to 59
days without any concomitant reduction in body weight.
Feeding strategy to reduce fat deposition in broiler chickens was
studied by Jones and Farrell (1989) and they reported early feed
restriction begining at 7 days old, decreased the body fat and extreme
feed restriction reduced the adipocyte volume but milder restriction
affected the adipocyte number.
The commercial broiler females had higher abdominal fat content
than males (Alsobayel et al., 1989). The effects of severe feed restriction
by providing diets containing the metabolizable energy value of 1.5X body
weight (kg)2/3 was studied by Liarn et al. (1991) and they concluded that
feed restriction for 5 or 10 days at 1 or 5 weeks old reduced the fat pad
weight by 31.3 to 70.8 per cent.
Ballay et al. (1992) studied the initiation and the length of different
feed restriction programs on broilers and reported that feeding regimen
had little effect on organ weights relative to body weight, amount of
abdominal fat or percentage lipid in the abdominal fat pad.
The feed restriction significantly reduced the abdominal fat
(Plavnik and Balnave, 1992). Susbilla et al. (1994) recorded non-
significant difference among different groups in percentage of carcass fat
and abdominal fat of broilers restricted to 50 or 75 per cent of ad libitum
intake from 5 to 11 days old.
A study on feeding of 90, 75 and 60 per cent of previous 24 hour
feed consumption of full fed controls from 7 to 14 days of age or 80 and
60 per cent from 8 to 16 days of age was conducted by Deaton (1995)
and concluded that the feed restriction did not affect the abdominal fat of
broilers.
The effects of feed restriction in broilers was studied by Santoso et
al. (1995) by way of providing 50 per cent ad libitum for 5, 10 and 15
days starting from 5 days old followed by ad libitum feeding up to 56
days old and reported that the abdominal fat weight tended to be
increased at 27 th day old and was decreased at 56th day.
Zhong et al. (1995) found that feed restriction of 1.49 Kcal/g BW2/3
daily from 7 to 12 days of age in broilers showed decreased abdominal fat
level than the control. They attributed it to the reduction in adipocyte
volume due to reduced lipogenesis.
A broiler experiment was conducted by Ramlah et al. (1996) by way
of providing feed ad libitum, restricted to 75 per cent of ad libitum intake
from 8 to 14 days old or restricted to 50 per cent of ad libitum intake
from 15 to 21 days old and concluded no effect on the weight of
abdominal fat.
The effect of long term feed restriction in broiler chicken was
studied by Khantaprab et al. (1997) from 1 to 50 days old i.e., fully fed,
20 and 40 per cent reduction in feeding and reported fat deposition
included abdominal, inter muscular and other parts of the body was
inhibited by feed restriction.
Attia et al. (1998) studied the effect of broilers subjected to feed
restriction during second week by 50 per cent of ad libitum control for
one week and 50 per cent of ad libitum during second and third week age
and reported a lower abdominal fat percentages in one week feed
restriction than the other two methods at 7 weeks of age. Females had
higher abdominal fat percentage than the males.
Broilers chicks fed with 85 or 75 per cent of ad libitum or ad
libitum for 5 days per week with 3rd and 5th days of food withdrawal for
28 days showed lower abdominal fat in 25 per cent feed restricted birds
than all the other groups (Benyi and Habi Habi, 1998).
Leeson et al. (1999) recorded low abdominal fat in broilers fed with
low nutrient density diets between 0 to 70 days of age compared to
control.
The effects of energy and protein dilution (adding rice hulls at 0,
100, 150, 200, 250 and 300 g/kg) in broiler chickens was demonstrated
by Yussefikelari Colaii et al. (2001) between 6 and 12 days of age and
reported diet dilution had no significant effect on abdominal fat
proportions.
Urdaneta Rincon and Leeson (2002) reported broilers restricted to
90 per cent of ad libitum intake of control group during different intervals
showed no significant difference in abdominal fat pad weight across
treatments.
The effects of three feeding levels (control, 15% and 30% below ad
libitum) during 7 to 14 days of age on broiler performance was
demonstrated by Shariatmadari and Vaeztorshizi (2004) and they found
there was no effect of restriction on abdominal fat content.
Broiler chicks were full fed from 7to 13 days of age or given 25 and
50 per cent of ad libitum intake on a daily basis (physical restriction) or
100 per cent of ad libitum intake on a daily basis, when the diets were
diluted with 25 and 50 per cent rice hulls (dilution restriction). The result
showed that method and severity of restriction had no effect on intestine
and liver weight but 50 per cent diet diluted birds showed significantly
lower abdominal fat pad compared to full fed birds (Toghiani et al.,
2004).
The feed restriction either in male, female or combined sex broilers
during 2nd and 3rd week of age by 10, 20 and 30 per cent to that of ad
libitum control feeding showed the abdominal fat deposition is lowered by
early feed restriction (Nirmala et al., 2005).
2.6 Effect of dietary variation and feed restriction on skeletal deformities
Salmon et al. (1983) studied the effect of starter and finisher
protein on performance, carcass grade and meat yield of broilers and
found that leg problems were associated with the highest starter protein
level.
Short term feed restriction during early stage benefits broiler
chickens by slowing early growth and allowing better skeletal
development (Robinson et al., 1989). Similarly Leeson and Summers
(1988) reported slower growth rate at early stage in broilers might also be
important for optimising skeletal development.
Robinson et al. (1992) showed that restricting feed intake of
broilers at 2nd week post-hatch significantly reduced skeletal problems
associated with early fast growth.
The potential of short term feed restriction programs as a
management tool, directed at decreasing the incidence of skeletal disease
in broilers (Yu and Robinson, 1992).
Broilers fed with reduced nutrient density (175 g protein/kg)
between 7 and 14 day of age showed feed restricted birds had
consistently fewer walking defects and less ‘hock burn’ than the ad
libitum fed birds (Carter et al., 1994). Feed restriction at an early age of
broilers reduced the mortality, leg abnormalities and ascites (Zubair and
Leeson, 1994a).
Deaton (1995) conducted a study on feeding of 90, 75 and 60 per
cent of previous 24 hour feed consumption of full fed controls from 7 to
14 days of age or 80 and 60 per cent from 8 to 16 days of age and
concluded that the deformed legs did not differ between any of the
comparisons.
Camacho et al. (2004) carried out an experiment by restricting feed
to the broilers for 8 hrs/day for 14 days at 21 or 28 day, 14 or 21 day
and 7 or 14 day of age and concluded that the quantitative feed
restriction at 7 days of age reduced the mortality from leg problems.
Feed restriction programs in broilers, both quantitative (60% of ad
libitum) and qualitative (energy and protein) between 7 and 14 days of
age did not significantly affect the Ca and P contents of tibia, femur and
humerus. However, bird age influenced Ca and P contents, with levels
increasing up to 28 days of age and remaining constant afterwards
(Giustibruno et al., 2004).
The effect of mealtime feeding (food was withdrawn from 9 am to 3
pm) and low protein diet feeding (19.5% protein) between 7 to 21 days of
age in broilers was studied by Konca et al. (2004) and found that feeding
programs did not improve the gait score of broilers.
2.7 Effect of dietary variation and feed restriction on Economics
Starr Jackson et al. (1982) reported feed costs per kilogram live
weight and return over feed costs per bird were significantly (P<0.01)
affected by dietary protein and energy levels. Increasing dietary protein
level above 20 per cent resulted in higher costs and lower returns.
Despite the low cost of the 16 per cent crude protein diets, production
costs were increased above those for higher protein levels, reflecting
the poor body weights and feed conversion ratio achieved with these
diets.
The performance of broiler chicks due to feed restriction was
studied by Plavnik and Hurwitz (1985) by way of providing energy from
30 to 45 Kcal/day for different periods ranging from 6 to 28 days started
at the age of one week and found an economic advantage in restricted
feeding over a continuous ad libitum feeding regiment.
Attia et al. (1991) conducted a study on broilers subjected to ad
libitum feeding or feed restriction to 50 per cent of control feed intake
between 1 and 3 weeks or given 20 per cent dried chicken excreta during
5 and 6 weeks age and concluded that incorporating dried chicken
excreta in finisher diets is economically feasible, whereas 50 per cent
feed restriction is not.
Mild food restriction applied at an age of about one week and
allowing for 60 to 75 per cent of normal growth, may offer an economic
advantage over a continuous ad libitum feeding regimen in broilers
(Plavnik and Hurwitz, 1991).
Tottori et al. (1997) reported the economic performance with
restricted feeding was better than that with full feeding as a result of
improvements in viability and feed conversion rates.
The effect of diets diluted with 0, 20, 40 and 60 per cent of rice
hulls between 7 and 14 days of age in broilers was studied by
Upendrakumar et al. (1997) and concluded that cost of production was
not affected by diet dilution.
Broilers subjected to mild feed restriction (90% of ad libitum intake
for 4 days) revealed some economic advantages as compared to control
birds mainly by reducing mortality (Lippens et al., 2000).
Nirmala et al. (2005) reported the feed restriction either in male,
female or combined sex broilers during 2nd and 3rd week of age by 10, 20
and 30 per cent to that of ad libitum control feeding showed the broilers
with 20 per cent feed restriction during 8 to 14 days of age fetched the
highest net profit per bird (Rs.10.08) and the highest net profit per kg live
weight (Rs.4.57).